Automatic choke control



I Nov. 29, ,1960

R. W. DURLER AUTOMATIC CHOKECONTROL Filed Aug. .5. 1957 INVENTOR, RUSSELL W. DURLER z-amzwm ATTORNEY United Sttes Patent AUTOMATIC CHOKE CONTROL Russell W. Durler, Flint, M ich., assignor to ACE Industries, Incorporated, New York, N.Y., a corporation of New Jersey 7 Filed Aug. 5, 1957, Ser. No. 676,326

Claims. (Cl. 123-119) This invention relates to carburetors for internal, combustion engines and, more particularly, to means for controlling the operation of a carburetor choke valve during starting and warming up of a cold engine.

Briefly, the present invention contemplates the provision of a carburetor having a choke valve controlled by an automatic choke device of the type in which a thermostatic element, such as a bimetallic strip, acts to close the choke valve when the engine is cold, and a piston acts responsive to manifold suction to open the choke valve upon starting of the engine. In the operation of conventional automatic choke devices of this type, during starting of a cold engine, the piston overcomes the resistance of the thermostatic element when the engine starts firing, and thereby opens the choke valve to reduce the richness of the fuel mixture supplied to the engine. By thus suddenly reducing the richness of the fuel mixture being supplied to a cold engine, theengine is often caused to stall. It is, therefore, an object of the present invention to provide an automatic choke device of the type described, in which the thermostatic element is effective to close the choke valve responsive to a predetermined drop in manifold suction, to thereby enrich the fuel mixture to prevent stalling of the engine.

Another object of the invention is to provide an automatic choke control device embodying means responsive to manifold suction for controlling the force exerted by the piston to open the choke valve.

A further object of the invention is to provide an automatic choke control device comprising a suction piston having an air bleed controlled by a check valve movable from a normally open position to aclosed position responsive to manifold suction during normal operation of the engine.

Another object of the invention is to provide an automatic choke control device adapted to be applied to various types of carburetors to facilitate starting of cold engmes.

The invention embodies other novel features, details of construction, and arrangement of parts, which are hereinafter set forth in the specification and claims, and illustrated in the accompanying drawing, wherein:

Fig. l is a vertical sectional view illustrating a carburetor provided with an automatic choke control embodying features of the invention.

Fig. 2 is a sectional view, taken along the line 2 2 of Fig. 1, and showing the connection between the choke control housing and a conventional manifold stove.

Fig. 3 is a detail top plan view showing the suction piston provided with an air bleed controlled by a check valve.

Figs. 4 and 5 are longitudinal sectional views taken along the lines 4.4. and 55, respectively, of Fig. 3.

Fig. 6 is a schematic view illustrating a modified form of the invention.

Referring now to the drawing for a better understanding of the invention, the automatic choke control is shown as applied to a conventional type of downdraft carburetor comprising an air horn section 6 having an air inlet 7, a main body section 8 having a mixing passage 9, and anoutlet section 11 having an outlet passage 12 for communication with an intake manifold ll) of an internal combustion engine, said sections being secured in assembled relationship by means of bolts or screws (not shown).

The main body section 8' is provided with a fuel bowl 14 in which the fuel level is maintained substantially constant by means of a conventional fuel inlet needle valve (not shown) controlled by a float 15. The main body section is also provided with a primary venturi 16, secondary venturi 17, and a main venturi 18 concentrically arranged within the mixing passage 9, the primary and secondary venturis being supported on the main body cy webs 19. The venturis are arranged, as shown in Fig. 1, whereby the primary venturi discharges a fuel mixture into the throat of the secondary venturi which, in turn, discharges into the throat of the mainventuri.

A main fuel passage 21 leads from the fuel bowl 14 to a main nozzle 22 adapted to discharge fuel into the throat of the primary venturi 16 during operation of the engine. Fuel for idling operation of the engine is supplied from the fuel bowl 14 to the main fuel passage 21, and thence through an idle orifice tube 23 and idle passage 24 to an idle port 26 disposed to discharge into the outlet passage 12 adjacent the edge of a throttle valve 25 when the latter is in its idling position, as shown in Fig. 1. The throttle'valve is secured to a shaft 26a journaled at its ends in the outlet section 11 and adapted to be manually operated. by means of a suitable linkage leading from an accelerating pedal to a throttle lever 27 secured to the shaft.

An unbalanced choke valve 28 is secured to a shaft 29 journaled at its ends in the air horn section 6. A choke housing 31 is provided on the air horn section to receive one end of the choke shaft having a choke control mechanism operatively connected thereto. A cover 32, formed of material having a relatively low coefficient of heat conductivity, is secured to the housing 31, with a partition 33 therebetween, by means of'screws 34;

The choke control mechanism is shown as comprising a bimetallic thermostat 36 having its inner end secured to a stud 37 mounted on the cover 32; Acrank 38 is secured to the choke shaft 29 and projects through a slot 39 in the partition. 33' for engagement by the outer end of the thermostat 36 to biasithe choke valve 28 toward its closed. position when the engine is cold.

A cylinder 41 is provided within the choke housing 31 to receive a piston 42 having a passage 43 extending axially therethrough to receive a tubular valve body 44 press-fitted therein. A ballcheck valve 46 is provided in the passage 43, and is urged against. a boss 47 on the piston by means of a helical compression spring 48 seated within the valve body 44; A connecting link 49 is pivotally connected. at one end thereof to the boss 47 and has its other end pivotally connected to thecrank 38, whereby downward movement of the piston, as illustrated in Fig. 1, acts to urge the choke valve 28 mward its open position.

A stove 51 having an air inlet 52 and air outlet 53 is mounted, on the exhaust manifold 54 of the engine to provide a source of heated air for the thermostat 36, said outlet being connected to an air inlet 56 leading into the choke housing 31 by means of a conduit 57. A passage 58 extends downwardly from the cylinder 41 below the piston 42 to a port 59 in the'wall of the outlet passage 12 posterior to the: throttle valve-25. A groove 61 is formed irrthe wall of the cylinder. 41 adjacent the piston 42 ,for. the. passage of heated air from the stove 51 and housing 31 through the passage 58 into the outlet passage 12.

In the operation of the automatic choke control mechanism to facilitate starting of a cold engine, the choke valve 28 is yieldably engaged against movement from its closed to open position by the thermostat 36. Upon firing of the engine during starting, air is drawn from the stove 51 into the choke housing 31, and thence through the valve body 44 and passage 58 into the outlet passage 12 to move the valve 46 against the annular seat 62 on the valve body, after which, suction in the outlet passage 12 will draw the piston downwardly through the cylinder to move the choke valve toward open position to lean out the fuel mixture to the engine. In the event the engine starts to stall due to the lean fuel mixture, the pressure in the outlet passage will rise and permit the spring 48 to unseat the check valve 46, and cause the thermostat to close the choke valve 28 to thereby temporarily increase the richness of the fuel mixture supplied to the engine.

In starting an engine during cold weather, the valve 46 may be seated and unseated several times, thereby automatically controlling the richness of the fuel mixture until the engine reaches a certain operating temperature; after which, the thermostat 36 will move to its retracted position and the choke valve will move to its full open position.

Fig. 6 is a schematic view illustrating a modified form of the invention in which a suction responsive valve 65 is interposed in a suction passage 6667 leading from the choke cylinder 41 to the mixture conduit 12 posterior of the throttle 25, the valve being shown as comprising a valve piston 68 mounted in a valve cylinder 69. The choke cylinder 41 is provided with a conventional choke piston 71 for operating the choke valve 28, and the wall of the cylinder is provided with a by-pass groove 61.

A compression spring 72 is provided to yieldably resist movement of the piston 68 in a direction to open the suction passage 6667. A hot air by-pass 73 leads from the passage 66 to the cylinder 69, and an auxiliary suction passage 74 leads from the cylinder 69 to mixture conduit 12 posterior of the throttle 25.

In this form of the invention, starting of the engine creates a relatively high suction condition posterior of the throttle 25 and causes the valve piston 68 to overcome the spring 72 and open the suction passage 66--67 to the choke cylinder 41. The choke piston is thereby urged in a direction to open the choke valve 28 against the resistance of the thermostat 36, to lean out the fuel mixture being supplied to the engine. In the event the engine starts to stall, the decrease in manifold suction permits the spring 72 to move the valve piston 68 to close the suction passage 6667. The thermostat 36 then acts to close the choke valve to thereby enrich the fuel mixture to the engine. During full throttle operation, hot air is drawn from the choke cylinder 41 through the by-pass 73, valve cylinder 69, and auxiliary passage 74 into the mixture conduit 12. The hot air by-pass 73 is closed by the valve piston 68 responsive to high intake manifold suction conditions.

While the invention has been shown in but two forms, it is obvious to those skilled in the art that it is not so limited but is susceptible of various changes and modifications without departing from the scope of the invention as defined in the claims.

I claim:

1. In an internal combustion engine having intake and exhaust manifolds, a downdraft carburetor having a mixture conduit communicating with said intake manifold, means to discharge fuel into said conduit, choke and throttle valves in said conduit, yieldable temperature responsive means urging said choke valve toward closed position when the engine is cold, means including a check valve responsive to intake manifold suction for moving said choke valve toward open position upon firing of the engine to decrease the richness of the fuel mixture, and

means to open said check valve responsive to a drop in manifold suction to cause said temperature responsive means to close said choke valve to increase the richness of the fuel mixture to prevent stalling of the engine.

2. Means for automatically controlling a carburetor choke valve during starting of an internal combustion engine, comprising means for urging the choke valve toward closed position to provide a rich fuel mixture when the engine is cold, other means responsive to manifold suction for urging said choke valve toward open position upon firing of the engine to lean out the fuel mixture, and means for rendering said other means inactive when the engine begins to stall whereby said choke valve is moved to closed position by said first-mentioned means.

3. Means for automatically controlling a carburetor choke valve during starting of an internal combustion engine, comprising a thermostat for urging the choke valve toward closed position to provide a rich fuel mixture when the engine is cold, other means responsive to manifold suction for urging said choke valve toward open position upon firing of the engine to lean out the fuel mixture, and means for rendering said other means inactive when the engine begins to stall whereby said choke valve is moved to closed position by said thermostat.

4. A device according to claim 3 where, said other means comprises a suction piston.

5. A device according to claim 3 wherein, said other means comprises a suction piston having an opening therethrough, and a check valve in said opening.

6. A device according to claim 3 wherein, said other means comprises a suction piston having an opening therethrough, a check valve in said opening, and a spring to open said check valve responsive to a predetermined decrease in manifold suction.

7. In an internal combustion engine having intake and exhaust manifolds, a downdraft carburetor having a mixture conduit communicating with said intake manifold, means to discharge fuel into said conduit, choke and throttle valves in said conduit, yieldable temperature responsive means urging said choke valve toward closed position when the engine is cold, means including a check valve responsive to intake manifold suction for moving said choke valve toward open position upon firing of the engine to decrease the richness of the fuel mixture, and a spring to open said check valve responsive to a drop in manifold suction to cause said temperature responsive means to close said choke valve to increase the richness of the fuel mixture to prevent stalling of the engine.

8. In combination with an automatic choke control for a carburetor, a choke valve, a suction operated piston for actuating said choke valve, said piston having an opening therethrough, and a valve in said piston to alternately open and'close said opening, said valve modifying the effectiveness of said piston.

9. In combination with an automatic choke control for a carburetor, a choke valve, a suction operated piston having an opening therethrough, and a check valve in said piston to alternately open and close said opening, said check valve being biased to open position by a spring and movable to closed position by air flow through said opening for modifying the effectiveness of said piston.

10. In an automatic choke control for a carburetor, a tubular piston, a tubular valve body mounted in said piston and having a valve seat, a valve movable against said seat responsive to air flow through said body, and a compression spring yieldably resisting seating of said valve.

References Cited in the file of this patent UNITED STATES PATENTS 

